Movement Execution Induces STDT Changes With Focal Dystonias

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Researchers concluded that alterations to the somatosensory temporal discrimination threshold caused by movement execution are not normal in focal dystonia.
Researchers concluded that alterations to the somatosensory temporal discrimination threshold caused by movement execution are not normal in focal dystonia.

Movement execution changes somatosensory temporal discrimination threshold (STDT) values in patients with different focal dystonias, according to study results recently published in Movement Disorders.

In healthy individuals, STDT values increase with movement execution because of sensory gating at the subcortical level. STDT is abnormally increased in patients with focal dystonias; however, the effect of movement execution on STDT in this population remained unknown. 

Researchers at Sapienza University of Rome wished to determine whether STDT changes induced by voluntary movement are normal in patients with different types of focal dysplasia. They recruited 71 patients with dystonia with a mean age of 57±14 years. Of these individuals, 24 had blepharospasm (BSP), 31 had cervical dystonia (CD), and 16 had focal hand dystonia (FHD). The patients with dystonia were age-matched with 39 healthy volunteers. Paired stimuli for the STDT were triggered with movement execution at onset and at time intervals afterward. Researchers analyzed the kinetic aspects of motor tasks to determine whether tactile input leads to changes in movement parameters. 

Movement execution gave way to higher and longer increases in STDT in patients with CD and FHD than in those patients with BSP or the healthy participants at the onset of movement execution and thereafter. Post hoc analysis revealed similar changes in STDT values for patients with FHD and CD (=.85). STDT values also changed similarly in patients with BSP and healthy participants (=.99).

STDT did not change the mean velocity of index finger movements in patients with dystonia when compared with healthy participants. Researchers conducted between-group repeated-measures analysis of variance and did not find significant factor interstimulus interval (F =0.38, =.68), group (F =0.6, =.52), or group vs interstimulus interval interaction (F =1.09, =.36). 

These results indicate that STDT changes brought about by voluntary movement are abnormal across multiple focal dystonias. Abnormalities varied by type of dystonia. Abnormal gating of sensory information is likely involved in voluntary movement-induced elicitation or deterioration of multiple types of focal dystonia. 

Reference

Conte A, Belvisi D, De Bartolo MI, et al. Abnormal sensory gating in patients with different types of focal dystonias [published online November 7, 2018]. Mov Disord. doi: 10.1002/mds.27530

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